Process of making tartaric acid.



JOHN MCDOUGALL, OF GREENWICH PARK, ENGLAND.

PROCESS OF MAKING TABTARIC ACID.

Specification Letters Patent.

Patented Sept. 8, 1908.

Application filed February 24, 1908. Serial No. 417.319.

To all whom it may concern:

Be it known that I, JonN MQDOUGALL, knight, a subject of the King of Great Britain, residing. at Clifton House, Greenwich Park, in the county of Kent, England, have invented certain new and useful Im provements in the. Manufacture of Tartaric Acid, of which the following is a specification;

In the manufacture of tartaric acid the acid is converted nto its calcium salt which is then decomposed by sulfuric acid. My invention relates to a process whereby this step, with its attendeut disadvantages, is avoided. For this purpose I obtain an alkali salt, preferz'rhl the potassium salt, of the acid and treat this with sulfuric acid so as to obtain a solution of alikali sulfate and tartaric acid. To this solution I then add a. suitable sulfate such as aluminium sulfate, in solid form or as a solution, so as to produce an alum in the solution. The alum is then separated from the tartaric acid by crystallization. I include an ammonium salt and double alkali salts in the term alkali salt. For instance, in treating lees, argol or tartar, sulfuric acid is added to the raw material to convert the potassium bitartrate into potassium sulfateandtartaricacid and whatcalcium tartrate may be present into calcium sulfate and tartaric acid. The liquid, after separa tion from any solid matter that may he present, is mixed with aluminium sulfate equivalent to the potassium sulfate that is to say in the proportion for forming alum, and the solution is concentrated to crystallize the alum, as many crystnllizations heing. effected as may he necessary to free the tartaric acid from alum. From the mother liquor in!- laric acid is cr 'stallized.

The following example illustrates the in- \-'ention:-LT5 tonso? nrgol of Tl per cent. strength containing-l5- pcr ccui. of calcium tartrulo,arc mixed wit h (2.4 ton of sulfuric acid of Si) per cent. strength diluted with H) timcs its volume of water. The mixture is heated to boiling win-rob) the whole of linlnrlralcs present become tartaric acid in accordance with the equations: 2KHCJ-LO ll,.S l-f. .(l ll,(),, K,SO, CaQlLO, H.,S( H.,( $1 0, CaSO The liquor is now filtered during which operation t he temperature should not be ailowed to fall below 80 C. so as to prevent the reformation of the sparingly soluble potassium bitartrati. The vegetable matter-and the calcium sulfate remain in the filter-and to the liquor is added aluminium sulfate in the form sayof alum cake, in sufficient quantity to combine with the whole of the potassium sulfate present to form alum, in accordance with the equation The liquor is now evaporated until its specific gravityis 1.4, whereupon alum crystallizes and is removed; after this the liquor is again concentrated to crystallize out a second crop of the remaining alum. llav- .ing thus separated all but traces of the alum the tartaric acid is crystallized and purified by recr ,"stallization while the filial mother liquors are worked up in a fresh operation.

Having tlms'descrihed the nature of this invention and thehcsi means l know of carrying the same into practical cil'cct, l claim In the manufacture of tartaric acid the process \rhicn consists in addine to a solution of an alkali salt of the acid, sulfuric acid so as to produce a sulfate of the alkali and lurlaric acid, then adding to the solution a suitable sulfate such as aluminium sulfate, so as to produce an alum in the solution. and finally evaporating to crystallize this alum, suhstauitially as described.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses. 

